Re: [patch] per cpu MCA/INIT save areas (take 2)

[Russ Anderson <rja@sgi.com>]

Keith Owens wrote:
> On Tue, 23 Nov 2004 17:36:41 -0600 (CST), 
> Russ Anderson <rja@sgi.com> wrote:
> >--- tonyluck2.6.10.new.orig/linux/arch/ia64/kernel/mca_asm.S	2004-11-17 16:22:30.041624520 -0600
> >+++ tonyluck2.6.10.new/linux/arch/ia64/kernel/mca_asm.S	2004-11-23 13:49:27.631179608 -0600
> 
> > 	rse_switch_context(r6,r3,r2);;	// RSC management in this new context
> >-	movl	r12=ia64_mca_stack
> >+
> >+	mov	r2=r12;;		// phys addr of MCA save area
> >+	addl	r2=IA64_MCA_STACK,r2;;
> >+	mov	r12=r2
> > 	mov	r2=8*1024;;		// stack size must be same as C array
> > 	add	r12=r2,r12;;		// stack base @ bottom of array
> > 	adds	r12=-16,r12;;		// allow 16 bytes of scratch
> > 					// (C calling convention)
> 
> Replace with mov r2=IA64_MCA_STACK+8*1024-16;; add r12=r12,r2;; plus suitable comments.

Looking closer at the original code, r12 is converted to PA, but isn't used 
after that, that I can see.  Could someone explain where r12 is used?


        // Setup new stack frame for OS_MCA handling
        movl    r2=ia64_mca_bspstore;;  // local bspstore area location in r2
        DATA_VA_TO_PA(r2);;
        movl    r3=ia64_mca_stackframe;; // save stack frame to memory in r3
        DATA_VA_TO_PA(r3);;
        rse_switch_context(r6,r3,r2);;  // RSC management in this new context
        movl    r12=ia64_mca_stack
        mov     r2=8*1024;;             // stack size must be same as C array
        add     r12=r2,r12;;            // stack base @ bottom of array
        adds    r12=-16,r12;;           // allow 16 bytes of scratch
                                        // (C calling convention)
        DATA_VA_TO_PA(r12);;

        // Enter virtual mode from physical mode
        VIRTUAL_MODE_ENTER(r2, r3, ia64_os_mca_virtual_begin, r4)
ia64_os_mca_virtual_begin:

        // Call virtual mode handler
        movl            r2=ia64_mca_ucmc_handler;;
        mov             b6=r2;;
        br.call.sptk.many    b0¶;;
.ret0:
        // Revert back to physical mode before going back to SAL
        PHYSICAL_MODE_ENTER(r2, r3, ia64_os_mca_virtual_end, r4)
ia64_os_mca_virtual_end:


Thanks,
-- 
Russ Anderson, OS RAS/Partitioning Project Lead  
SGI - Silicon Graphics Inc          rja@sgi.com